The present invention is a spring that is designed to bend along its longitudinal axis and conform to a spring conformance surface that is substantially either convex or concave along the entire portion that the spring is meant to conform to. The spring conformance surface that the spring is designed to conform to may also have greatly varying radii of curvature along the portion that the spring is intended to conform to. Springs that can be bent along their longitudinal axis to conform to such spring conformance surfaces are known. An example of such a prior art spring is shown in FIG. 1. In FIG. 1 the prior art spring is shown in a bent state as it would be disposed when it were installed and conformed to a spring conformance surface such as the underside of a hood of a vehicle which is shown in FIG. 1. Surface conforming springs of the prior art can be of a number of different constructions. Most surface conforming springs have a longitudinal axis central to a body of the spring and sectional planes disposed perpendicular to the longitudinal axis. The cross-section of surface conforming springs is generally either the same through all of the sectional planes of the surface conforming springs or the same at sectional planes which are spaced at repeating intervals along the longitudinal axis of the surface conforming spring. Surface conforming springs that have such a constant or repeating cross-section generally have a relatively constant stiffness against bending along the longitudinal axis of the surface conforming spring. Most surface conforming springs are constructed such that the longitudinal axis is straight when the surface conforming spring is in its free state. One of the most common types of surface conforming springs of the prior art, which is shown in FIG. 1, is constructed of wire which is woven laterally within a single plane along the longitudinal axis of the surface conforming spring. Such a spring has a constant stiffness in all respects from a first end of the spring to a second end of the spring.
Most surface conforming springs are maintained against the spring conformance surface in the same, simple manner. The first end of the surface conforming spring is engaged to a first mounting point adjacent the spring conformance surface and the second end of the spring is engaged to a second mounting point adjacent the spring conformance surface. An inter-mounting point line is a straight line between the first mounting point and the second mounting point. The length of the inter-mounting point line is generally less than a spring free length which is the length of the surface conforming spring in its free state. An inter-mounting point curve is defined by the intersection of a plane, in which the surface conforming spring is generally disposed when the surface conforming spring is engaged to the first mounting point and the second mounting point, and the spring conformance surface. When the surface conforming spring is mounted to the first mounting point and the second mounting point adjacent a concave spring conformance surface, the surface conforming spring bows away from the inter-mounting point line toward the spring conformance surface. For spring conformance surfaces that are concave, the length of the inter-mounting point curve is generally equal to or less than the spring free length. This is so that, when the surface conforming spring is mounted the surface conforming spring will expand against and closely conform to all portions of the spring conformance surface including those portions which have a small radii of curvature. For spring conformance surfaces that are convex the length of the inter-mounting point curve is generally equal to or greater than the spring free length. This is so that, when the surface conforming spring is mounted the surface conforming spring will be drawn against and closely conform to all portions of the spring conformance surface. As was mentioned above, most surface conforming springs of the prior art were constructed such that they had a relatively constant stiffness along the entire length of the longitudinal axis of the spring. The stiffness that the surface conforming springs could have was also limited by a number of factors. These factors include but are not limited to the ability of a person to elastically deform the spring during mounting and the amount of pressure which the surface conforming spring could exert on the spring conformance surface without damaging the spring conformance surface.
The limits that were imposed upon the stiffness of the surface conforming spring effected the performance of the surface conforming springs within their intended function. Surface conforming springs as described above are generally used to hold objects between the surface conforming spring and the spring conformance surface. An example of this is shown in FIG. 1, which is an exploded view of an assembly for holding sound insulation to the underside of a hood of a vehicle. The surface conforming spring of FIG. 1 is intended to hold the sound insulation to the underside of the hood. As is the case with many such systems, in which a surface conforming spring is employed to hold an object against a spring conformance surface, the surface conforming spring is of a constant and limited stiffness. Because of its limited stiffness the surface conforming spring shown in FIG. 1 is prone to bowing away from the spring conformance surface due to the pressure exerted on the surface conforming spring by the sound insulation. The assembly for holding the sound insulation to the underside of the hood must, therefore, include structure other than the surface conforming spring to aid in holding the sound insulation against the underside of the hood. Such difficulties are common with assemblies that utilize surface conforming springs that are of a constant stiffness that must be limited by the factors described above.
In view of the above mentioned constraints it is an object of the present invention to provide a surface conforming spring and a mounting structure therefore that is stiff enough to firmly hold an object against a spring conformance surface. It is a further object that the surface conforming spring of the present invention conforms closely to all portions of the spring conformance surface along an inter-mounting point curve. Finally it is an object of the present invention that the surface conforming spring is relatively easy to mount and that it does not exert excessive pressure on the spring conformance surface.
The above mentioned objects of the invention as well as others not mentioned are satisfied as follows. The present invention is a surface conforming spring that has variable stiffness along a longitudinal axis of the surface conforming spring. The surface conforming spring is constructed such that some portions of the surface conforming spring are stiffer against bending along the longitudinal axis than other portions. The surface conforming spring is constructed such that portions of the surface conforming spring which will be adjacent portions of the spring conformance surface that have relatively large radii of curvature have a relatively high stiffness against bending. The surface conforming spring is also constructed such that portions of the surface conforming spring which will be adjacent portions of the spring conformance surface which have a relatively small radius of curvature have a relatively low stiffness against bending. The surface conforming spring described above will readily conform closely to the spring conformance surface and will be stiff enough against bending at those portions where the spring conformance surface has a large radius of curvature to firmly hold objects against the spring conformance surface.
The surface conforming spring and the mounting assembly therefor are also constructed such that the surface conforming spring can be easily mounted. The surface conforming spring has at each end a mounting engagement structure for engagement to one of the mounting points disposed adjacent the spring conformance surface. Each complimentary pair of a mounting point and a mounting engagement structure may be comprised of one female mounting member and one male mounting member. To mount the surface conforming spring an installer must simply elastically deform the surface conforming spring into a shape similar to that which it assumes when mounted and engage the mounting engagement structures of the surface conforming spring to the mounting points. The internal forces and bending moments present in the surface conforming spring then help maintain it in its installed position. Thus, it can be seen that the present invention meets the objects outlined above as well as others not mentioned.